1. Field of the Invention
The invention relates generally to efficient means for the generation of electrical or other power utilizing energy from subterranean geothermal sources and, more particularly, relates to novel arrangements including efficient deep well heat exchange and pumping equipment for application in deep hot brine wells for the transfer of thermal energy for use at the earth's surface.
2. Description of the Prior Art
A basic advance in the geothermal power extraction art, not limited to use with the rare dry steam geothermal sources and also devoid of the steam and geothermal brine separation problems and the consequent corrosion problems attached to prior art systems using mixed steam and hot water supply wells was presented in the H. B. Matthews U.S. Pat. No. 4,142,108, issued Feb. 27, 1979, entitled "Geothermal Energy Conversion System".
The aforementioned patent discloses a geothermal energy recovery system of improved efficiency which makes use of thermal energy stored in hot, solute-bearing well water as it is pumped upward to the earth's surface through an extended heat exchange element for continuously heating a downward flowing organic fluid to a supercritical state. Some of the energy of the latter fluid is used within the well for operating a turbine-driven pump for pumping the hot, solute-bearing well water at high pressure and always in liquid state to the earth's surface, where it is reinjected into the earth in another well. The temperature difference between the upward flowing brine and the downward flowing organic fluid is maintained finite in a predetermined manner along the subterranean extended heat exchange element. After driving the deepwell turbine-driven pump, the organic fluid arises to the earth's surface in a thermally insulated conduit; at the earth's surface, vapor turbine electrical power generation equipment is driven by the heated organic fluid which is then returned into the well for reheating in the extended heat exchanger.
A major advance of the above described system over prior art geothermal energy conversion system resides in the deep well heat exchange element wherein the pressure and temperature of the downward flowing organic fluid increases continuously, due to the gravity head pressure and the heat transfer with the upward flowing brine, respectively, and are manipulated by the apparatus of the invention, such that the specific heat characteristic of the organic fluid may be adjusted to achieve the most efficient heat transfer between the organic fluid and the brine.
The temperature characteristics of the particular source of brine, however, may be such that the most efficient heat transfer between a particular organic fluid and the brine is not attainable. For example, the source of brine may be characterized as having insufficient temperature, and if so, there will be a loss of efficiency. Moreover, it is highly probable that even an ideal source of brine may "cool off" and exhibit insufficient temperature conditions once it has been exploited for a substantial period of time. Accordingly, it is neither practical nor desirable to adapt each gravity head system to accommodate a different type of organic working fluid depending upon the temperature and/or pressure conditions of a particular source of brine.